1. Field of the Invention
The present invention relates to an observation apparatus for observing positions of optical fibers and a fusion splicer using the same for optical fibers.
2. Related Background Art
A conventional observation apparatus for optical fibers is disclosed in Japanese Laid-open Patent Application No. 1-107218. The conventional observation apparatus for optical fibers described in this application is an apparatus for illuminating light from obliquely above to a plurality of optical fibers fixed in a row on a support frame and for picking up an image of the neighborhood of end faces at spliced portions of the optical fibers illuminated by the light, through a TV camera located obliquely below.
FIG. 9 is a drawing to show an optical system according to a conventional observation apparatus for optical fibers. As shown in FIG. 9, an image pickup plane 100 of a TV camera is located normally to the optical axis 102 of optical lens 101 and the optical system is adjusted so that the focus is achieved on the image pickup plane 100 intersecting with the optical axis 102. Accordingly, the focus deviates with increasing distances from this position, causing the image to be blurred; therefore, the number of the optical fibers for which the image could be displayed in a screen was limited to four pairs if their outside diameter portions were to be measured with the accuracy of several .mu.m or less.
Incidentally, the observation apparatus for optical fibers was often incorporated in the fusion splicer for optical fibers. In that case, observation was carried out prior to fusion splicing so as to check whether an offset of axis or the like occurred between optical fibers to be fused and spliced with each other. Recently, the number of pairs of optical fibers to be spliced at one time with an fusion splicer for optical fibers has been increased, in order to increase the efficiency of splicing of optical fibers. At present, the technology for fusion-splicing twelve fiber pairs at one time is established, and the technology for fusion-splicing sixteen fiber pairs or twenty four fiber pairs at one time is also under research and development.